1. Field of the Invention
The present invention relates to a technique for processing images, and more particularly, to a technique for detecting an object in an image.
2. Description of the Background Art
Various techniques have been developed to identify an object (target) in a captured image by using an edge extraction process. For example, Japanese Unexamined Patent Publication No. 2002-288798 (hereafter referred to as “Patent Literature 1”) describes a technique for identifying (extracting) a target with high accuracy in a different image with a different contrast between a target (e.g., an automobile) and its background (e.g., a parking place). With the technique described in Patent Literature 1, the image in which edges have been extracted is subjected to predetermined processing assuming the background includes more image areas with low brightness than the target. With this technique, the captured image first undergoes an edge extraction process to generate an edge extracted image. The pixel values of the edge extracted image are then divided by the brightness values of the original image to generate an image in which edges have been enhanced. Even for an image in which the contrast between a target and its background is low, such edge enhancement generates an edge enhanced image including appropriately enhanced edges when the background includes more image areas with low brightness. With the technique described in Patent Literature 1, the target is identified (extracted) from the edge enhanced image. This enables a target to be identified (extracted) with high accuracy in a different image with a different contrast between a target (e.g., an automobile) and its background (e.g., a parking space).
However, the technique in Patent Literature 1 assumes that the background includes more image areas with low brightness, and thus may fail to identify (extract) an object (target) in an appropriate manner in an image with a particular background. The technique in Patent Literature 1 may also fail to detect the contour of a target in an appropriate manner in an image in which the target and its background have almost no contrast in a predetermined direction of the image. This may disable an object (target) to be identified (extracted) in an appropriate manner.
It is an object of the present invention to provide an object detection apparatus, a program, and an integrated circuit that enable the contour of a target to be detected (estimated) in an appropriate manner even in an image in which the target and its background have almost no contrast in a predetermined direction of the image.